Oil recovery refers to the process by which crude oil is extracted from beneath the Earth's surface. Oil recovery can be divided into three phases: Primary, Secondary and Tertiary. The primary phase production uses the reservoir's natural energy (fluid and rock expansion, solution-gas drive, gravity drainage, and aquifer influx) to produce oil. This phase allows about 5% to 10% of the oil in the reservoir to be extracted.
In the secondary phase production, also named as “secondary recovery”, a water-flooding process uses water injection to increase the production from the oil reservoir. Secondary recovery allows an additional 25% to 30% of the extracted oil from the reservoir. However, even after a long term water-flooding process, some amounts of oil still remain trapped in the reservoir due to a high capillary pressure.
The aim of the tertiary phase recovery of oil is to recover crude oil remaining after the primary and secondary oil recovery. In this phase different materials are injected together with water to improve the flow between oil, gas and rock. In this phase, an additional 20% to 30% of the oil in the reservoir can be extracted.
It is known that the interfacial tension (IFT) between crude oil and water should be significantly very low for a successful enhanced oil recovery. This can be achieved using surfactant flooding. Generally, the main requirement of surfactant processes is targeting of ultralow interfacial tensions. For this purpose, the right surfactant should be selected and evaluated at low and economic concentrations. On the other hand, maintaining low interfacial tension during the displacement process is a critical challenge because of dilution and adsorption effects in the reservoir.
The presently known technologies suggest the use of various materials and processes such as CO2 injection, surfactant agent injection, natural gas miscible injection, and steam recovery, in particular, during the tertiary oil recovery phase. In this phase the injection of different materials improves the flow between oil, gas and rock, and to recover crude oil still remaining after the primary and secondary oil recovery phases. Oil that is left behind after water flooding is still present because either it has not been contacted by the injected fluid, or because of the presence of the capillary forces that exist between oil, water and the porous rock in the contacted portions which trap and retain said oil.
It is known in the state of the art the use of surfactant agents that are introduced into the reservoir to increase oil recovery by lowering the interfacial tension between oil and water. Trapped oil droplets are mobilized due to a reduction in interfacial tension between oil and water. The coalescence of these drops leads to a local increase in oil saturation. An oil bank starts to flow, mobilizing any residual oil in front. Eventually, the ultimate residual oil is determined by interfacial tension between the oil and surfactant solution behind the oil collection.
Nowadays, methods for improving oil recovery, in particular those concerned with lowering the interstitial oil saturation, have received a great interest in the industry. There are many different types of chemical compositions used in the oil recovery process involving the individual or combined injection of surfactants that lower the surface interfacial tension between the injected water and crude oil in the reservoir and/or change the wettability of the reservoir rock surface, allowing the desorption of crude oil. During the past several decades, various methods have been sought in order to efficiently increase the secondary and tertiary oil recovery process, while improving the economic viability and efficiency of operations. Examples of said methods include, but are not limited to, chemicals, polymer, surfactant and alkaline flooding techniques. Although said methods have been shown to be responsible in decreasing the interfacial tension while increasing the sweep efficiency, there is still a need for enhanced oil recovery from the reservoirs, in particular where such oil recovery process should be carried out from high salinity and high temperature of oil reservoirs. Most of the available surfactants used in oil recovery operations are either ineffective at a high level of salinity hardness of the water, or incapable to stand the higher temperatures of many processes.
Therefore there is a need to provide a method for an efficient secondary and tertiary water flooding of heterogeneous oil reservoirs at high salinity and high temperature. In particular there is a need to provide a novel composition able to improve oil recovery from reservoirs by efficiently reducing interfacial tension while increasing the volumetric sweep efficiency of fractured and/or heterogeneous oil reservoirs.